<正>为了每年提供造林新需的具有生活力的种子及长期保存种质资源，贮藏种子是必要的手段。种子寿命具有遗传性，且因树种而异。种子的贮藏特性可以分成5类：正常型、亚正常型、温带顽拗型、热带顽拗型和中间型。种子含水量和贮藏温度是影响种子贮藏是否成功的两个最重要因素。但因树种及其贮藏特性不同，种子含水量和贮藏温度的最适值也不同。为了保持正常型和亚正常型种子的生活力，这类种子必须密封贮藏；但对顽拗型种子，因其需要保持种子的代谢活性及要进行有氧呼吸，则需要气体交换。

Three methods (Box-counting method, The two-surface method and Berezovskava method) which were applied to estimate fractal dimension of poplar crown were compared in this study. The two-surface method was of heavy work and complexity. Berezovskava method was proved to be unsuitable for estimating fractal dimension of poplar crown due to its inaccuracy. In spite of limitation to 2-dimension, it is safe to say that Box-counting method was the best way to estimate fractal dimension of poplar crown owing to its easy operation, rapidity, high repetition, good stand for crown structure and foliage distribution. There was no link between fractal dimension of crown and crown shape, crown size, but a significant correlation was found between fractal dimension and foliage. Generally, the larger the foliage is, the bigger the fractal dimension is.